1. Field of the Invention
This invention relates to a holding structure of substrates utilized in the tuners of television sets and the like or home converters for the same.
2. Description of the Prior Art
The conventional holding structure for mounting and grounding multiple layers of printed circuit substrates will be described with reference to FIG. 3 which is a sectional view showing a grounding structure of the conventional multiple substrate assembly. A first printed circuit substrate 1 and a second printed circuit substrate 2 are piled one upon another, and conductive patterns 3, 4 are provided, respectively, on the upper face of the first printed circuit substrate 1 and on the under face of the second printed circuit substrate 2. Reference numerals 5, 6, 7, 8 are thru-holes bored respectively in the conductive pattern 3, first printed circuit substrate 1, second printed circuit substrate 2, and conductive pattern 4. Through these thru-holes 5, 6, 7, and 8 an electric part 9 is passed with both ends being secured by solder 10, 11 to the conductive patterns 3, 4 of the first and second printed circuit substrates 1, 2. Further, on the first printed circuit substrate 1 a grounding conductive pattern 12 is provided, and, correspondingly, a grounding conductive pattern 13 is provided on the second printed circuit substrate 2. Reference numerals 14, 15, 16, and 27 are holes formed respectively in the conductive pattern 12, first printed circuit substrate 1, second printed circuit substrate 2, and conductive pattern 13, into which a thru-hole pin A is inserted. This thru-hole pin A passes through the holes 14, 15, 16, 17 and projects on the first and second printed circuit substrates 1, 2 and its ends are secured by solder 18, 19. One end of the conductive pattern 13 is secured by solder 21 to a chassis 20.
Because grounding of the first and second printed circuit substrates is achieved, as shown in FIG. 3, a thru-hole pin is needed, which increases the number of parts. Further, the grounding conductive patterns 12, 13 must be set in fixed alignment with the first and second printed circuit substrates 1, 2. Thus, the degree of freedom in designing other circuit patterns is limited, shielding between the first and second printed circuit substrates 1, 2 is impossible, and grounding efficiency is inferior because the grounding path is led out by means of the narrow grounding conductive pattern 13 to the chassis 20 and soldered at 21.
Also, because the substrate 2 and the chassis 20 have different coefficients of thermal expansion, fractures in the solder 21 securing them together can be easily formed.